Conversion of hydrocarbons



G. W. 'ROBINSON I'AL .CONVERSION OF HYDROGARBONS May 13, 1941.

Filed June 15, 1937 INVENTORS.

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- Patented May 13, -1941 UNI-TED@ STATUE s PATENT OFI-icaAv aurait CONVERSION OF HYDROCARBONS George W. Robinson, Houston, lIlex., and George Roberts, Jr., Montclair, N. J., vassignors to The Polymerization Process Corporation, Jersey 1 City, N. J., a corporation of Delaware i Application June i5, 1931, serial Nu.'14s,274

a cians (ferias-1o) This invention relates to the production of nor-l mally liquid hydrocarbons, including gasoline or motor fuel constituents, from normally gaseous hydrocarbons. More particularly, the invention relates to a process for effecting the conversion of hydrocarbon gases, such as those produced in oil Cai cracking operations or from natural gas sources,

to hydrocarbons of higher boiling point suitable perature of 750 to 1250 F. at pressures in excess of 400 pounds per square inch, or by heating them to higher temperatures and lower pressures, or by heating them at lower temperatures in the presence of suitable catalysts.v The products of such conversion operations, which may be the result of polymerization or related reactions. in-

clude hydrogen, normally gaseous hydrocarbons,

and normally liquid hydrocarbons including those which form constituents of gasoline.

In carrying out such va conversion operation the conversion products are ordinarily fractionated to produce' a normally gaseous fraction and a normally liquid fraction. The normally liquid fraction is removed for treatment to recover gasoline therefrom, and the normally gaseous fraction is further fractionated to recover any hydrocarbons suitable for further conversion treatment. These hydrocarbons are combined with `similar yhydrocarbons from an extraneous source 4 zone wherein conditions are maintained to effect the separation therefrom of a'liquid fraction and agaseous fraction predominating in hydrogen' and methane. Liqueed normallyl gaseous hydrocarbons may be introduced into this Zonato-'- charging stock of superior quality and to etliciently recover from such gases substantially all the constituents thereof desired orA suitable for conversion to normally liquid products. It is an object of the present invention to produce anl improved operating method and cycle for .carrying out a recycling type of gas conversion process including such additional operating'results as may be found to obtain.

The invention contemplatesthe treatment of stream of normally gaseous hydrocarbons under pressure by the application of heatto effect conversion-of at least a portion thereof to normally liquid hydrocarbons and; the separation 'of the conversion products into normally liquid and nor.

mally gaseous constituents in two stages. In the first stage the conversion vproducts are maintained under conditions of temperature and pressure to effect separation of a gaseous fraction predominating in the lower-boiling normally gaseous hydrocarbons and a liquid fraction consisting of normally liquid constituents and a substantial proportion' of the higher-boiling'normally I vgaseous constituents of the conversion products.

The gaseous fraction is passed to a separating Yassist in the separation. The liquid fraction separated in this separating zone consists substantially entirelyof those normally gaseous hydroand subjected therewith to further conversion treatment. f l This invention contemplates the separation of normallyA liquid from normally gaseous constituents in conversion reaction products of the nature described above, under conditions which provide emcient recovery of normally liquid constituents,

efficient separation of convertible constituents from the normally gaseous products of conversion, and a system which permits the use of a liquid stream, withdrawn from the products of conversionand containing convertible constituents,

foruse as a cooling medium for admixtu're with Y the products of conversion to cool the latter. `The invention.' also contemplates -preliminary treatment of hydrocarbon gases; from any suitable vsource such as natural gas, or gases produced in oil'cracking, such as the overhead'gas from a high-pressure -separator or the reiiux from a gasoline stabilizer, or both, to obtain therefrom a carbons most suitable for conversion operations, and from this frac'tion may be drawn the stream undergoing ,conversion treatment, as described above. y

A portion of theliquid fraction consisting of `normally liquid -hydrocarbons containing dissolved therein normally 'gaseous hydrocarbons separated in the irst stage of separation of the conversion products, described above, may be adofnormallyliquid and normally gaseous hydro-' carboris is effected. The normally gaseous hydro-` "carijlons,v containingsubstantially no incondensi bles.. may be liquefied and passed to the separat-v .aration thereof to'cool the latter.

mixed with the conversion products before sep- 'l'he remainder ofthe liquid fraction separated in thevflrst -stage of separation may be passed to a` second stage of separation wherein separation ing zone to assist inthe separation of the gaseous :fraction predominating in the hydrogen and methane, and, incidentally, tov furnish part ofthe .conversionreaction charge. The separating zone "pressure conditions to effect stabilization oi the liquid fractionvthcrein which constitutes conversion charge by stripping from it gases undesired for conversion treatment.

The normally liquid fraction separated in the second stage may be further fractionated to separate: therefrom a gasoline fraction or may be withdrawn for treatment with liquid products oi oil cracking. l

The two-stage separation or" .-the conversion products is preferably accompiished under lower pressure than that which obtains in theconversion reaction with the second stage being maintained under substantially lower pressure than that in the first stage. The iirst stage of separation, however, may be carried out at or only slightly below the conversion reaction pressure. The fresh feed to the system may consist of gaseous hydrocarbons from any of the sources mentioned'above. According to the present inventio'n a stream of such normally gaseous hy- -f drocarbons is separated into a liquid fraction,

consisting of liquefied normally gaseous hydrocarbons, which is introduced to the separating Zone, and a gaseous fraction which is introduced to a scrubber or absorber for the recovery oi convertible constituents remaining in the gases. To this scrubber or absorber also is introduced the gaseous fraction predominating in hydrogen and methane Yseparated in the separating zone. The K gases from these sources pass through the absorber or scrubber in intimate contact with liquid absorbent medium such as a gas oil. The enriched absorbent medium is withdrawn. from the scrubber and stripped, preferably in two stages, `oi the normaily gaseous hydrocarbons dissolved therein. These hydrocarbons are liquefied and introduced into the separating Zone to assist in the separation therein of the gaseous fraction predominating in hydrogen and methane and to furnish part oi the conversion charge.

The dry gases, scrubbed of .convertible constituents, are withdrawn from the scrubber and ezrpandedthrough a work engine to drive va conis presser acting-on the fresh gas feed for thesystem. Y

, IThe invention is illustrated in the accompanying drawing in which the `ligure is a diagrammatic view in elevation oi ,apparatus suitable for carrying out the present invention. t is to be understood, however, that the drawing is illustrative only, the invention being capable of other modifications which may be beyond the physical limitations of the apparatus indicated. In the drawing a heater i which may be of any suitable construction, ractionating towers 2 5 3 and absorber tower E, strippers E and 7, furnace charge stripper accumulator 9, and gasoline collector id are indicated, together with auxiliary equipment ior carrying out theA process. Fresh feed, which may includenatural gas or gases produced in oil cracking operations, or both, is introduced to the system through line il bymeans of compressor i?. `Additional gases which may be already under high pressure, such as those recovered in a high-pressure separator oi oil-cracking products, may be introduced to the system; without the use of the compressor I2 through line i3 which connects with line H beyond the compressor. The gases so introduced under pressure are cooled by passage through cooler li located in line ii with iiqueiaction of higher-boiling normally gaseous hydrocarbons. The cooled and partially liquefied stream is introduced to a separator l5 in which the liqueed fraction, which preferably predominates Ain Cs and C4 hydrocarbons, is collected as liquid. This liquid is withdrawn from separator l5 through line l5 by means or" pump i1 and introduced into a furnace-charge stripper B.

The uncondensed gases separated in separator i5 are withdrawn through line IB and introduced into an absorber tower 5 wherein they are' scrubbed jointly with gases from furnace-charge stripper which also are introduced into absorber tower 5 by means of line i9 which connects with the upper portion of furnace-charge stripper In absorber tower 5 the gases pass upwardly in countercurrent with descending liquid absorbent medium, which suitably may be gas oil or gasoline. duced into the upper portion of the absorber tower 5 through line 2d, after being cooled in cooler 2i located in line 2B. As the gases ascend thel absorber tower 5 in intimate contact with the descending absorbent medium a final recovery oi desired convertible constituents contained in the gases is effected, these constituents being.

dissolved in the absorbent medium. The scrubbed gases are withdrawn from absorber tower 5 through iine Si and thus may be passed' from the system, or all or a portion thereof may be diverted from line Se through line and expanded through a work engine connected to drive compressor i2. The expanded cooled gases may then be used for cooling purposes in other parts of the system. In addition tocompressor i2 a second compressor 5'! may be provided to "replace Vor supplement compressor i2; Compressor di is located line $5 connected at both ends to line ii. Valve il@ located .in line ii between the ends or line St may be closed, and valve 29 in line St may be opened to 'divert the iced through line et and compressor Ell.

Coolers 2i. and :23 are connected with the absorber tower 5 at intermediate portions thereof to cool portions of the descending absorbent medium which are circulated through the coolers and back to the absorber tower c, through lines 25. and 2f', respectively.A In this manner the heat of absorption is removed from the absorbent medium, and maximum absorption of convertible constituents is accomplished.

The enriched absorbent medium .collects in the bottom ci absorber tower d and is maintained at a temperature substantially higher than that obtained in the portions of the absorber tower wherein contact of liquids and gases occurs. As a result of the substantially higher temperature maintained in the enriched absorbent medium in thebottc'm of absorber tower 5 partial stripping of absorbed gases from the absorbent-medium is obtained. This serves to remove from point adjacent the point of introduction of the gases from separator I5 and `furnace-charge lstripper 8.' This lmay be accomplished by the The absorbent medium is intro-V 'gases by subsequent stripping operations.

provision of va lline 26 provided with a cooler "2l which withdraws gases from the tower at a point above the liquid level in the towerand substantially below the pointof introduction of the vgases to be scrubbed, coolsthe gases so v'vithtower 5 at the place of introduction of the gases to be scrubbed. -The higher temperature desiredin the liquid in the bottom of the absorber.

tower 5 niay be vobtained by circulatinga porscrubbed. The absorbent medium so collected drawn and re-introduces them into the absorber tion of this liquid'in heat exchange with a suitis circulated through a heat exchanger 29 by means of line 30 which connects with the absorber tower 5 at points above ,andl below the plate 28.v With tower 5 maintained, for example,

1".' at 400 pounds per square inch pressure, the temperature in that portion where gas and liquid contact occurs 'may be maintained at about 100 F. while the temperature'of the liquid in the bottom may be kept at about 190 F.

. The maintenance of the absorber tower l under v the temperature'conditions described above permits the most eiiicient use of 'the absorber tower by providing contact of absorbent medium and mitting th'e use lof a relatively small quantity of absorbent medium. AtA the same time it prevents the inclusion in the absorbent medium withdrawn from tower 5 of diicultly condensibl'e gases, such as methane', and permits individual I control of the nature and quantity of hydrocarbons ,dissolved in the absorbent medium withdrawnl from the 4tower-5 by means of regulation of the temperature maintained in the bottom of the tower 5. Furthermore, the maintenance lof the lower temperature in the upper-portion of i the scrubber or absorber tower minimizes loss of` lighter constituents of the liquid absorbent medium 'through vaporization in the gases Withdrawn through line 94.

gases at a relatively low temperature, thus pr- Enriched absorbent medium is withdrawn from absorber tower 5 by means of line 3l which passes through heat exchanger 32 and, if necessary, heater 33, to raise the temperature of the absorbent medium in preparation for the Subscquent stripping operation. yFrom line 3l the` heated enriched absorbent medium is introduced into a primary stripper 6 in which a portion .of

the hydrocarbons dissolved 4therein is separated.

The separated gases ascend to the top of primary stripper 6, and the partially impoverished absorbent medium collectsv in the bottom of primary stripper 6 where it maybe heated, if desired, to eii`ect further-removal` of dissolved gases therefrom'. This heating may be accomplished by collecting aportion of the descending absorbent medium in trap-out tray 34 andcirculating the liquid so collected through h eat exchanger 35, in indirect contact with the previouslymentioned recirculated impoverished absorbent medium, and back to the primary stripper 6 at a point below the trap-out tray 34, by means of line 36. The primary stripper 6 is maintained at conditions oi temperature and pressure to l 4effect stripping from the absorbentf 'medium of t. the lighter gases dissolved' therein such as the C; hydrocarbons. For example, when maintaining the stripper 6 under a pressure of about 375 cooler 45.

y 3 pounds per square inch thebottom temperature may be about 375 F. with a top temperature of about. 90 to 100? F, to prevent loss of absorbent medium by vaporization in the gases.

The partially impoverished absorbent medum, iswithdrawn from the bottom of primary strip.

per 6 through line 31 and introduced into a secondary stripper 1 at a` reduced pressure, for

example, 150 pounds per square inch, the reduction in pressure being accomplished by means of valve 38 located in line 31. A heater 39 may also be provided in line 3l to heat the partially limpoverished absorbent medium passing there- 'dissolved therein. For example, at 150 pounds per square inch pressure a bottom temperature of about 550 F. may be employed with a' top.

temperature of about 110 to prevent loss of absorbent medium.

1 The substantially completely impoverished absorbent medium is withdrawn from secondary stripper 1 through line 20, and its sensible heat may be utilized to heat enriched or only partially impoverished absorbent medium in heat exchangers 35, 32 and 29 which are connected with line 20,

' and, 'as stated above, the recirculated absorbent medium may be cooled in cooler 2l prior to introduction to absorber tower 5. A pump 4l may be provided in line 20 to circulate the impoverished absorbent' media through line 20 into absorber tower 5 zagainst the-higher pressure maintained therein; Additional absorbent medium may be introduced to the system, to replaceany losses,

through line 42 which connects with line 20 in front of pump 4I.

The normally gaseous .hydrocarbons separated from the absorbent medium in secondary stripper 'I ascend to the top thereof and are withdrawn therefrom through line 43 and passed'thereby to condenser 44 for liquefaction.

y The normally gaseous hydrocarbons separated from the absorbent vmedium in primary stripper 6 ascend tothe top therebf and are withdrawn therefrom by means of line 46 which` includes a Liqueed normally gaseous hydrocarbons condensed in condenser 44 are withdrawn therefrom and admixed with the gases passing through line' 46 prior to their admission to cooler 45 bymeans of line 41 which is pro- .sulting mixture, permits easier condensation and then facilitates the substantially complete oo nden'sation ofthe gases in cooler 45. From line 46 the substantially condensed gases are introduced to separator 49 yin which any uncondensed` f gasesare separated and are'witlidra'wn overdenser 44. v completely condensed together with the gases head through line 50, which connects the separator 49 with the line 43in which gases from the top' of secondary stripper l are passed to con- In condenser .44 thesel gases are from secondary stripper l.

A portion of the liqueed normally gaseous hydrocarbons from condenser it may be withdrawn from line il and returned as redux to secondary stripper 1 through line 5i to maintain the desired low top temperature in the stripper l.

are withdrawn through line .id by means of pump and introduced to heater i after being preheated by heat exchange with the hot products of conversion in heat exchanger lt is to be understood, of course, that additional liquefied normally gaseous hydrocarbons may be' introduced to accumulator g from an extraneous Source, for example, by means of line 59.

in the heater i the normally gaseous hydrocarbons introduced therethrough are maintained under conditions of temperature and pressure 'suitable for conversion of at least a portion thereof of normally liquid hydrocarbons. The conditions of conversion will depend upon the nature of the liquid desired and the constituents of the charge thereto. For example, the hydrocarbons may be heated to a temperature or 759 to 1250 F. under pressures of at least eo'pounds per square inch, such as between 400130 3000 pounds per square inch. As a specific example, they may be heated under a pressure of 1200 pounds per square inch to'an exit temperature of 1030" F.

The products of conversion are withdrawn from heater i by means of lined@ and may be'admixed with a cooling liquid introduced to line 6d through.

Thereafter pressure is reduced, if necj' line Gi. essary or desired, by means of valve 62 in line 6D, and the mixture of cooling liquid and conversion products is further cooled by passage p through heat exchanger 58 in indirect contact with the incoming charge. The mixture of conversion products and cooling liquid may be further cooled by heat exchange and, if desired, by a final cooler 63 in its passage through line 60 from which it is introduced into primary fractionating tower 2. l

Primary fractionating tower 2 is maintained at l elevated pressure which may, however, be subl stantially lower than the pressure maintained in heater `I. For example, the temperature. of the products entering primary fractionating tower 2 will determine largely the pressurenecessary to effec-t the separation of gases desired. However,

decimi? solved in the normally liquid hydrocarbons which collect in the vbottom of the tower 2. A portion oi these normally liquid hydrocarbons containing dissolved therein relatively high-boiling normally gaseous hydrocarbons is withdrawn from tower 2 through line 6! by means of pump $4 and admlxed with the hot, products vof conversion emerging from the heater i through line 60, This serves to cool the hot products of conversion to prevent over-conversion.

The gases separated in primary fractionating tower 2 predominating in hydrogen and methane andthe more difdcultly convertible hydrocarbons such as the C2 and Ca hydrocarbons are withdrawn from the tower 2 by means of line o5 and introduced to condenser 6E wherein a portion thereof may be liqueed for return by means oiv line 6l to fractionating tower 2 as reflux to assist in the separation' desired therein. The uncondensed gases are withdrawn from condenser 66 through line G8 and passed to condenser 'in which a further liqueiaction of a portion of the gases is accomplished. The'liquefled normally gaseous hydrocarbons are Withdrawn from oondenser 69 through line l0 and introduced into the top of furnace-charge stripper 6.l The uncondensed gases are withdrawn from condenser 69.

through line 1| and introduced to furnace-charge stripper t at an intermediate portion therein.

In furnace-charge stripper 3 conditions of pressure and temperature are maintained to stabilize the furnace charge which is introduced therein through lines i6, 52-and 10 and eiect a scrubbing of the convertible constituents still remaining in the gases introduced through line 1l. For example, the stripper '8 may be maintained at a pressurey of approximately 600 pounds with a top temperature of 85 F. and a bottom temperature 011180" F. The 'top temperature iseft'ected by v the temperature and quantity` of liquids introduced through .lines 1 6 and 52 and is regulated by the degree of cooling eiected in condenser 69. Suitable heating. means may be providedin thel bottomof stripper 8 tolmaintain the desired temperature in the liquids collected therein. Advantageously, a portion of the liquids in the bottom of the stripper 8-may be passed in indirect heat exchange with the products of conversion passing through line 60 in heat exchanger 12. Trap-out tray 13 may be provided in the furnace-charge' stripper 8 to collect a. portion of the descending liquid. The collected liquid is withdrawnfrom trap-outtray 13 through line 14 and circulated through heatl exchanger 12 wherein it, isheated to the desired degree and returned to'iurnacecharge strippers at apoint below trap-out tray 13. a The liquids containing dissolved therein normally gaseous'consttuents collected in thebottom of the primary fractionating tower 2 are withdrawn therefrom through line 15 and, if

-desired, through rcooler 1G located linv line 15 and' 'introduced' into secondary fractloiiating tower 3 it is feasible to cool tbe mixture of conversion f products and cooling fluid to a temperature of 4 approximately 225 F. before admission to thev ,primary fractionating tower 2, and at this temperature a pressure of 600 pounds per square inch is satisfactory for accomplishing the desired separation ofrgafses from the said mixture. PrimaryA fractionatng tower 2 ls operatedtoseparate from the products therein Aa gaseous fraction-predominating in hydrogen and methane and other dimcultly convertible hydrocarbons, leaving the major y proportion ofthe most Veasily convertible hydrocarbons such as the C; and -Cr hydrocarbons disat a pressure substantially lower than that obtaining in tower 2, the reduction in pressure'being eected conveniently by means or valve 11 located in line 1 5. In the secondary. fractionating tower 3 conditions 'of temperature and pres- 4sure are maintained to separate normally gaseous constituentsiromv normally liquid constituents.

The conditions of operation'for the secondary fractionating tower 3 will depend upon the op.- eration desired, the character of the material under-A treatment and the conditions of opera' tionof primary fractionating' tower 2. However, in connection with the conditions of opin which they pass to a condenser 19 wherein,

due to the fact that the gases consist substantially entirely of the relatively high-boiling normally gaseous hydrocarbons, the stream is entirely liqueed. The liquids are withdrawn from condenser 19 through line 8|! by means of pump 8| located'at line 8U and admixed with the liquefied, normally gaseous hydrocarbons passing through line 52 to the furnace-charge stripper 8. A portion of the liquefied gases withdrawn from condenser 19 through line 80 may be diverted from line 80 through line 82 for return to the top of the'secondary fractionating tower 3 as reux to assist in maintaining the proper temperature therein.,

The liquid. fraction separated in secondary fractionating tower 3 collects ln the bottom of the tower and may be heated by any suitable heating means such as heater 83 to drive 'off normally gaseous hydrocarbons dissolved therein. These liquids are then Withdrawn from the bottom of tower 3 through line 84 and introduced to a'gasoline -fractionating tower 4 after being cooled, if desired, by passage through cooler 85 located in line 84. The fractionating operation in gasoline-fractionating tower 4 may be accomplished at a lower pressure than that ob! taining in tower 3, in which case the reduction in a single structure provided with suitable trapout trays and other necessary connections.

The invention has beendescribed ywith refer 'Y ence to a speciric mdication illustrated byM stood, however, that the invention is not t o be` limited by the specific modiication or specic apparatus described but is capablef of other embodiments which maybe beyond the physical limitations -of the apparatus illustrated inthe drawing.

We claim:

- 1.A The method of converting normally gaseous hydrocarbons to normally liquid hydrocarbons.

which comprises heating a stream of normally gaseous hydrocarbons u'nder pressure to ei'ect conversion thereof intonormally liquid hydrocarbons including gasoline. constituents, thenl separating said stream under pressure into a liquid fraction consisting of the normally liquid hydrocarbons and relatively high boiling normally gaseous hydrocarbons and a normally gaseous fraction predominating in the relatively low boiling normally gaseous constituents there; of, passing said normally gaseous fraction to a separatory zone to separate therefrom a fraction- 1 predominatingin hydrogen and methane, witnmally drawing from said separatory zone liqueiied norgaseous hydrocarbons' substantially strippedof hydrogen and methane and combining at leastV a' portion thereof withlsaid stream undergoing conversion, separating said liquid in pressure may be conveniently effected by means of valve 86 located in line 84. In gasolinefractionating" tower 4 a gasoline fraction is separated overhead as vapor, and the remainl ing heavier liquids collect in the bottom of the tower. These liquids may be heated by heating means 8'! to effect a complete separation of gasoline, and the heated liquids may then be with- 'drawn from secondary 'fractionating tower 4 through line 88 for further treatment elsewhere. The gasoline vapors overhead are withdrawn through line 89, condensed in cooler 90 and collected in gasoline collector I0 from which they may be withdrawn from the system through line 9| by means of pump 92 located in line 9i. A portion of the gasoline liquid may be diverted from line 9| through line 93 for return as refluxvto the top of gasoline fractionating tower 4 to assist in -maintaining the proper temperature conditions therein. These temperature conditions are dependent entirely upon the nature of the cut desired and the pressure obtained.

fractiony under reduced pressure into'normally gaseous constituents and normally liquid constitunts including gasoline constituents, passing the gaseous fraction predominating in hydrogen and methane from said separatory zone v through a scrubbing zone under pressure, introducing into said scrubbing zone and into intimate contact with said gases passing therethrough a liquid absorbent medium whereby convertible constituents remaining in said gases` are dis'- solved in said absorbent medium, removing enr riched absorbent medium from said scrubbing zone, stripping and recovering normally gaseous hydrocarbons from said removed enriched ab- Fractionating towers 2,3, 4, Strippers 6, 1 and 8 and absorber tower 5 are provided with suitable bubble caps or plates or other suitable gas and-liquid contact means for assisting in the condensation. evaporation, absorption, stripping and -other'operations incidental to fractionation. It is apparent also that various pieces of equipment which are here indicated individually in order to simplify presentation of the, subject matter may be combined in unitary structures.

4li'or example, strippers 6 and 'l maybe combined fin a unitarystructure while the functions of Iractionating towers3 and 4 may be combined sorbent medium, introducing said recovered normally gaseous hydrocarbons into said separatory zone, introducing into the system from an extraneous source a stream of normally gaseous hydrocarbons, withdrawing scrubbed gases from said scrubbing zone, expanding said .scrubbed gases, utilizing the expansion of said scrubbed gases to effect compressionof said stream of said normally gaseous hydrocarbons from an extraneous source, cooling'said compressedV stream to eiect separation therefrom of a liquid fraction, and introducing at least a part of said last-men .tioned liquid fraction into said separatory zone to assist in said separation therein. Y f

2. The method of treatinga gaseous stream'v containing normally gaseouslhydrocarbons having at least .two carbon atoms per molecule -to eiect conversion thereof to normally liquid hydrocarbons, which comprises compressing said gaseousstream, cooling said compressed stream to effect separation thereof' into a gaseous fraction and a, liquid fraction predominating in relatively high boiling' normally gaseous-hydrocarbons, introducing vsaid liquid fraction into a sep'-y aratory zone wherein liquefied normally gaseous hydrocarbons are fractionated to strip therefrom 1 low boiling constituents, withdrawing from said separatory zone liqueed normally gaseous hy-` drocarbons substantially` stripped of low boiling constituents, subjecting at least a. portion of the liquefied ncrmaily gaseous hydrocarbons withdrawn from said separatory zone to conversion conditions of temperature and pressure to effect conversion of a portion thereof to normally'liquld l products, fractonating the conversion products to eiect separation thereof into gaseous constituents and a liquid product, introducing gasecus constituents thus fractionated from the conversion products into said separatory zone to effect separation thereof into a normally gaseous fraction predominating in hydrogen and methane and a liquefied fraction suitable for further conversion treatment, withdrawing from said separatory zone said gaseous fraction predominating in hydrogen and methane, introducing said lastmentioned gaseous fraction and the gaseous frac. tion separated rom the first-mentioned stream of normaliy gaseous hydrocarbons into a serubfrom said scrubbing zone, expanding said withdrawn scrubbed gases, and utilizing the expansion of said scrubbed gases to effect compression of said rstfmentioned gaseous stream.

GEORGE W. ROBDTSQN. GEORGE ROBERTS, JR. 

